INTRASPECIFIC AND INTERSPECIFIC COMPETITION BETWEEN SEEDLINGS OF ARTEMISIA-HERBA-ALBA ASSO AND ANTHYLLIS-HENONIANA BATT, CHAMEPHYTES OF PRESAHARIAN TUNISIA

Intra- and interspecific competition between seedlings of two presaharian chamephytes was experimentally studied. For the two species raised separately we found an increase in interspecific competition with increasing density. In the mixed culture, Artemisia herba-alba competes better than Anthyllis henoniana for water, with an increase of mortality rate and a decrease of the biomass of Anthyllis henoniana being observed. Modelisation of changes in the mortality rate allow us to discern between three factors (date, treatment and density) those responsible of the mortality during soil drying. For Artemisia herba-alba the date and density effects explain the evolution of mortality rate, for Anthyllis henoniana the model includes interactions between the three factors.